1. Field of the Invention
The present invention relates to a sample cooling device which cools a sample before analysis in an analyzer such as a liquid chromatograph analyzer.
2. Description of the Related Art
A sample cooling system of a sample cooling device which cools a sample before analysis includes a direct cooling system and an air cooling system. In the direct cooling system, a sample rack in which a sample container which stores therein a sample is set is placed on a sample rack placing unit that has been cooled to thereby directly cool the sample container through the sample rack (see Japanese Unexamined Patent Application Publication No. 2000-74802 and Japanese Unexamined Patent Application Publication No. 2001-12839). In the air cooling system, air inside a sample storage is cooled and circulated by a cooling Peltier element to thereby cool the entire air inside the sample storage (see Japanese Unexamined Patent Application Publication No. 2005-233867). The sample rack placing unit of the direct cooling system includes a sample rack cooling plate for directly placing and cooling the sample rack thereon, a Peltier element which cools the sample rack cooling plate, a heat dissipation fin which dissipates heat from the Peltier element, and a heat insulating material which blocks thermal conduction from components other than the Peltier element. The sample rack cooling plate is placed inside the sample storage, and the heat dissipation fin is placed outside the sample storage.
Since the direct cooling system can directly cool only the sample rack, the time required to reach a desired cooling temperature is advantageously short (that is, the cooling efficiency is excellent). However, on the other hand, since only the sample rack is cooled, moisture contained in the air inside the storage condenses on the cooled sample rack. In order to prevent such a problem, a dehumidification mechanism is provided. In the dehumidification mechanism, another Peltier element (hereinbelow, referred to as a dehumidification Peltier element) is provided to forcibly cause the moisture contained in the air inside the storage to condense on a dehumidification cooling plate which is cooled by the dehumidification Peltier element. Further, the condensate is collected in a tray, and the collected condensate is discharged to the outside of the storage through a tube or the like to thereby dehumidify the air inside the storage.
Such a sample cooling device includes one that constitutes a sample injection device of an analyzer such as a liquid chromatograph analyzer and one that is used for storing a sample separately from the sample injection device. The present invention is directed to both of the sample cooling devices.
The sample cooling device is designed so that the airtightness inside the storage of the device becomes as high as possible in order to prevent condensation in a sample rack cooling unit. However, when the sample cooing device constitutes the sample injection device, a mechanism that moves and cleans a sampling needle for sample injection is provided inside the storage of the device. Therefore, inside the storage are formed: a hole for discharging therethrough a cleaning liquid; a hole for discharging therethrough a leaking liquid; and a gap as a leak path such as a notch for passing therethrough a channel pipe or a wire. The leaking liquid is generated, for example, when a channel switching valve for introducing a sample for analysis into an analysis channel is exhausted, and the leakage of a mobile phase solvent thereby occurs.
Also in the sample cooling device that does not constitute the sample injection device, an outlet through which condensate condensing on the dehumidification cooling plate (heat transfer member) which is cooled by the dehumidification Peltier element is discharged to the outside of the storage serves as the leak path.
The inside of the storage of the sample cooling device communicates with the outside air through such a leak path, and therefore, cannot be completely sealed. Therefore, even when the dehumidification mechanism operates, the outside air flows into the storage from the outside thereof through the leak path, and the humidity inside the storage thereby increases. As a result, condensation may occur in the sample rack cooling unit, the sample rack, and the sample container.